For several years Galileo kept his word and continued his experiments and discussions without publicly advocating heliocentrism. Then he received the welcome news that Cardinal Maffeo Barberini had been named Pope Urban VIII. Barberini was a scientific “progressive,” having fought to prevent Copernicus’s work from being placed on the index of prohibited books. Equally significant, Barberini was a fan of Galileo and had even written a poem eulogizing him. Galileo was confident that now he could openly preach heliocentrism. But the new pope’s position on the subject was a complicated one. Urban VIII held that while science can make useful measurements and predictions about the universe, it cannot claim to have actual knowledge of reality known only to God. This theory, which sounds a bit strange, is actually quite close to what some physicists now believe, and as we shall see, it is entirely in line with Kant’s philosophical demonstration of the limits of reason.
So when Galileo in 1632 published his Dialogue Concerning the Two Chief World Systems, the church found itself in a quandary. First, Galileo claimed to have demonstrated the truth of heliocentrism, but in fact his proof was wrong. One of Galileo’s main arguments was that the rapid motion of the earth around the sun was responsible for the ocean tides. This was questionable at the time, and we now know that the moon is primarily responsible for tides. Galileo also assumed, as did Copernicus, that planets move in circular paths, even though by Galileo’s time Kepler had shown that the planetary orbits are elliptical. Galileo contended that Kepler was wrong.
Second, Galileo embarrassed the pope by constructing his “dialogue” between two figures, one representing himself and the other representing the pope. To dramatize the contrast, Galileo gave his pope character the name Simplicio, which in Italian means “simpleton.” The dialogue basically consists of foolish claims by Simplicio elegantly refuted by the character speaking for Galileo. The pope was not amused.
Galileo’s third mistake was that his writings were not confined to scientific issues; he also advanced his own theory of scriptural interpretation. Galileo argued that the Bible was largely allegorical and required constant reinterpretation to excavate its true meaning. The Jesuits had warned him not to venture into this territory. Scripture, they told Galileo,is the province of the church. With the hubris and imprudence not unknown among great men of science, Galileo ignored this counsel. So when he was again reported to the Inquisition, his opponents were able to fault him not only on scientific grounds but also on the grounds that he was undermining the religious teaching of the church.
Finally, this was the age of the Reformation. Protestant thinkers were attacking the Catholic church for not taking the Bible seriously enough. Urban VIII was eager to demonstrate the Vatican’s fidelity to scripture, and geocentrism was an interpretation on which there was agreement in the official positions of both Catholics and Protestants. Had the Reformation occurred a century before or after, Richard Blackwell writes, “the Galileo affair would probably not have happened.” Under the prevailing circumstances, however, the pope agreed to let the Galileo case proceed.
In 1633 Galileo returned to Rome, where he was again treated with respect. He might have prevailed in his trial, but during the investigation someone found Cardinal Bellarmine’s notes in the files. Galileo had not told the Inquisition—actually he had not told anyone—of his previous agreement not to teach or advocate Copernicanism. Now Galileo was viewed as having deceived the church as well as having failed to live up to his agreements. Even his church sympathizers, and there were several, found it difficult to defend him at this point.
